Resilient retaining means for digging implement blades



Dec. 12, 1967 A. PETERSEN 3,357,117

RESILIENT RETAINING MEANS FOR DIGGING IMPLEMENT BLADES Filed Dec. 14,1964 5 Sheets-Sheet 1 I37 A 7' TORNE) Dec. 12, 1967 G. A. PETERSEN3,357,117

RESILIENT RETAINING MEANS FOR DIGGINC' IMPLEMENT BLADES Filed Dec. 14,1964 5 Sheets-Sheet 2 llof I 36a 27a (IZQ 50 X I INVENTOR. ,fl A 17GERALD A. PETERSEN A TTORNE) Dec. 12, 1967 A. PETERSEN 3,357,117

RESILIENT RETAINING MEANS FOR DIGGING IMPLEMENT BLADES Filed Dec. 14,1964 5 Sheets-Sheet 3 f zsb 36 b WZOb 56\ A 52b l 2 b [2b (\NW INVENTOR.I 3/ GERALD PETERSEN 37b 28b BY H ATTORNEY Dec. 12, 1967 G. A. PETERSEN3,357,117

RESILIBNT RETAINING MEANS FOR DIGGING IMPLEMENT BLADES Filed Dec. 14,1964 5 Sheets-Sheet 4 \526 BYGER/ILD ,4. PETE/65y 42 c 37: 28:: a

' A r TOR/VEV Dec. 12, 1967 A. PETERSEN 3,357,117

ENT BLALLS RESILIENT RETAINING MEANS FOR DIGGING IMPLEM 5 Sheets-Sheet 5Filed Dec. 14, 1964 E INVENTOR. GERALD A. PETERSEN United States PatentOfiice 3,357,117 RESILIENT RETAINING MEANS FOR DIGGING IMPLEMENT BLADESGerald A. Petersen, Sunnyvale, Calif., assignor of one= half to Anita E.Petersen, Saratoga, Calif. Filed Dec. 14, 1964, Ser. No. 418,073 12Claims. (Q1. 37-142) This invention relates to a new and improvedresilient retaining means for digging implement blades. The resilientretainer is compressed between the blade and its holder and providesfrictional resistance to unintentional disengagement of the parts.

The present invention has particular application the removable blades ofearth digging machines, such as graders, dippers, back hoes, harrows,scarifies, cable plows, and similar equipment wherein the blade issubjected to heavier stresses and generally is larger than the removableteeth to which the resilient retainer principle has heretofore beenapplied. In heavy equipment of the type to which this invention is mostapplicable, a tooth formed with a hollow or recess is driven into orover a shank attached to a permanent part of the machine. The bladefrictionally engages the shank, or is welded thereto, or various keysare used to hold the parts in place, or one of the mating parts isdeformed as by swedging, dimpling, staking, or the like. The forcesapplied to the blade in use tend either to drive the blade so firmlyinto engagement with the shank as to make it difficult, if notimpossible, to separate when replacement of the blade is required, or,on the other hand, tend to separate the two parts by reason of theextreme and unpredictable stresses to which the blade is subjected. Inaccordance with the present invention, a resilient retainer iscompressed between the blade and the shank, with an extended area ofsurface contact between the insert and the two parts which it engages,so as to frictio-nally hold the blade on its shank against unintentionaldislodgment despite extreme stresses tending to separate the parts. Onthe other hand, since the resiliency of the insert is an importantfeature of the invention, the forces tending to prevent dislodgment ofthe two members when it is necessary to replace the blade are largelyovercome and it is merely necessary to apply suificient force in theproper direction to overcome the frictional resistance.

Accordingly, it is a principal purpose of the present invention toprovide means for retaining a blade on a permanent portion of a machinein such manner that it may be removed and sharpened, replaced, orotherwise repaired, and yet to provide a secure enough retention toprevent unintentional separation.

A particular advantage of the present invention is the facility withwhich the blade may be installed and removed and the fact that nospecial tools or other equipment are required for such purpose.

Still another advantage of the invention is the fact that the resilientinsert which secures the blade on its holder accommodates minorvariations in the construction of the blade and holder and thereby makesclose tolerances of dimensions of the mating parts unnecessary, andfurther accommodates wear of parts with passage of time.

In one form of the invention, hereinafter described in detail, theresilient retainer is inserted in a hole in one of the mating partsextending outwardly from the hole so that it is contacted by the othermating part when the two members are forced together. The exposed end ofthe resilient insert is bent ito a groove formed in one of the parts andcompressed between the bottom of the groove and the adjacent wall of thefacing member. The cross-sectional shape of the groove is substantiallydifferent from the initial unstressed shape of the resilient insert3,357,117 Patented Dec. 12, 1967 and hence there is considerabledeformation of the insert which increases the area of surface contact.Hence the frictional resistance to unintentional dislodgment of theblade from the holder is increased.

Another principal feature of the present invention is the fact thatneither bolts, metal keys, nor similar fasteners, nor welding to securethe blade on the shank are used, thereby eliminating a considerableamount of the difiiculty heretofore occasioned in securing blades totheir holders and removing the blades from the holders when required.

Other objects of the present invention will become apparent upon readingthe following specification and referring to the accompanying drawingsin which similar characters of reference represent corresponding partsin each of the several views.

In the drawings:

FIG. 1 is an exploded perspective view, partly broken away in section,showing a blade, holder and resilient insert, in accordance with onemodification of the invention.

FIG. 2 is a side elevational View of the structure of FIG. 1, inassembled position.

FIGS. 3 and 4 are sectional views taken substantially along the lines 33and 44, respectively of FIG. 2.

FIGS. 3A and 4A are views corresponding to FIGS. 3 and 4 of amodification.

FIGS. 5 to 8, inclusive, are views similar to FIGS. 1 to 4,respectively, of a modification.

FIGS. 9 to 12, inclusive, are views similar to FIGS. 1 to 4,respectively, of still another modification.

FIGS. 13 to 16, inclusive, are views similar to FIGS. 1 to 4,respectively, of a still further modification.

FIG. 17 is a perspective view of a harrow tooth, holder and associatedelements.

FIG. 18 is an enlarged side elevational view of blade and holder inassembled position.

FIGS. 19 and 20 are sectional views taken substantially along the lines1919' and 2020, respectively, of FIG. 18.

FIGS. 19A and 20A are and 20 of a modification.

FIG. 21 is a sectional view taken substantially along the line 21-21 ofFIG. 20.

In the form of the invention shown in FIGS. 1 to 4, blade 11 is of atype suitable on heavy equipment of the type of road graders, rippers,dipper buckets, and other machines where blades of comparatively largesize and heavy in weight are used and are subjected to severe stressesin unpredictable directions. A shank or a holder 12 is secured by meansforming no part of this invention to a permanent part of the equipmentand the blade 11 is held relative to shank 12 at an angle best suitedfor the performance of its function, such as that shown in FIG. 2. Thelower end 13 of holder 12 is bent generally parallel to the workingportion of blade 11 and then extends upwardly in a stretch 14 at anangle to portion 13.

views similar to FIGS. 19

curved to reduce resistance to the performance of the function of blade11.

The shape of blade 11 is subject to considerable variation. In the formof the invention herein illustrated, the distal portion is formed withflat, broad, top and bottom surfaces 17, 18, top surface 17 beingparallel to the direction of the tooth and the bottom surface 18tapering upwardly to a broad, blunt, transverse, forward end 19. Theproximal end of blade 11 has a downward extension 21, which is T-shapedin cross-section, extending longi tudinally of the tooth. Morespecifically, extension 21 has a leg 22 depending from the center of thebottom of blade 11, and its lower end is provided with a pair of J)outwardly extending feet 23. The bottom surface 24 of extension 21 ispreferably flat, as are the sides of leg 22, whereas the corners 26 arerounded.

In the form of the invention of FIGS. 3 and 4, a hole 27 is formed,extending transversely through leg 22, adjacent the rearward end of thetooth and approximately midway between the underside of blade 11 andlegs 23. Forwardly of hole 27 along the flanks of leg 22 are grooves 28.The cross-sectional area of each groove 28 is substantially less thanthe cross-sectional area of hole 27. The depth of groove 28, as measuredhorizontally in FIG. 3, is substantially less than the width of groove28, as measured vertically, and said width is substantially greater thanthe diameter of hole 27. The reason for these dimensions in thepreferred form of the invention will hereinafter appear.

The forward upper portion of extension 13 of holder 12 is slottedcomplementary to extension 21, in that it is formed with a top opening31, having substantially parallel side edges 32 and widening out tolateral extensions 33. The distance between sides 32 is only slightlygreater than the thickness of leg 22. The rearward end 34 of opening 31is curved upwardly so as to provide an abutment for the rearward end ofblade 11 when the blade is forced into holder 12, as shown in FIG. 2.Ordinarily, the fit between the mating parts is such that the blade andholder readily could be withdrawn relative to each other, if no lockingmeans were employed.

Frictionally to hold the two parts together in assembled position,resilient insert 36 is used. Insert 36 is formed of a resilientmaterial, preferably an elastomeric material such as neoprene syntheticrubber. However, natural rubber, other synthetic rubber, nylon cord,latex dipped nylon cord, soft iron wire, or other resilient substancesmay be used. The cross-sectional shape of insert 36 in its initialdimensions are slightly less than the corresponding dimensions of hole27, so that the insert 36 may be slipped through hole 27 and extendtransversely relative to the leg 22, perpendicular to the direction ofinsertion of the blade in the holder. The length of insert 36 ismaterially greater than the width of leg 22, so that in its positionextending through hole 27 it projects outwardly to either side of leg22. Accordingly, when blade 11 is pushed into holder 12, the exposedends of insert 36 are engaged by end 30 and bent into grooves 28. Byreason of the cross-sectional shape of groove 28, relative to theinitial or uncompressed shape of insert 36, the exposed portions 37 aredeformed to the shapes shown in FIGS. 3 and 4, conforming generally tothe shape of grooves 28. The length of grooves 28 in a longitudinaldirection is sufficient to accommodate the distortion of insert 36. Itwill further be seen, particularly with reference to FIG. 3, that thearea of surface contact of deformed portion 37 with side edges 32 ofholder 12 is of extended scope, as compared with what such area would beif the grooves 28 were less shallow and wide. Hence the frictionalresistance to withdrawal of the tooth on the holder is augmented.

Once the tooth is inserted in the holder in the position shown in FIG.2, the resistance against separation of the two members is very greatdespite the size and weight of the blade 11, and despite all forcestending to separate the two, many of which may, in use of the equipmenton which the blade is installed, come from unexpected angles. Further,since the blade is held in its holder by the resilient insert 36, it isnot necessary to make the clearance between the parts so tight that theforce of digging action jams the blade into its holder so that it cannotbe withdrawn. All that is necessary to separate the two parts is to hitthe end 20 of the blade in a longitudinal direction from the rear with ahammer or other tool until the frictional resistance to separation isovercome.

FIGS. 3A and 4A show a modification in which tooth and holder are of thesame shape as in the preceding modification, but hole 27 and grooves 37are eliminated. Corresponding parts are marked with the same referencenumerals. Transverse holes 127 are formed in end 13 directly oppositelegs 22 adjacent the front terminus of end 13. Longitudinal grooves 128are formed in sides 32 extending rearwardly of holes 127. Thedimensional relationship between grooves 128 and holes 127 is as in thepreceding modification. A resilient insert 136 is placed in one or bothholes 127 and is deformed into the shape indicated by reference numerals137 and function as in the preceding modification.

Turning now to the modification of FIGS. 5 to 8, inclusive, therelationship of the part is quite similar to the preceding modification,except that the shape of the mating portions of the tooth and holder arereversed. Since many of the parts are substantially identical,corresponding elements are designated by the same reference numeralfollowed by the Sllfi'lX a.

The proximal end of blade 11a is thickened and formed with a slot 41which is T-shaped in cross-section. In other words, the walls 42 of slot41 at the bottom are spaced relatively close together, with shoulders 43above top edge 42 and laterally widened-out portions 44 on either sideabove shoulders 43, with a substantially flat top wall 46.

Grooves 51 are formed in the sides of the lower end of portion 13a ofholder 12a to provide an H-shaped crosssection the upper part of whichfits inside opening 41 with a fairly close tolerance. Thus the shape ofportion 13a is such that there is a web 52 between grooves 51 ofrestricted width with lateral extensions 53 above web 52. It will beseen, particularly with reference to FIG. 7, that blade 11a is formedwith inward projections 54 which fit into the space of grooves 51, withwalls 42 in close engagement with the sides of web 52. The bottom 59 ofportion 13a engages under projections 54.

Hole 27a extends transversely through web 52, adjacent the forward endthereof. Rearward of hole 27a, grooves 28a are formed in the side wallsof web 52. Grooves 28a have a cross-sectional shape similar to thecorresponding grooves 28 in the preceding modification, and the relationof the cross-sectional area of the grooves relative to thecross-sectional area of hole 27a is similar.

When the blade 11a is forced over the projecting end 13a of holder 12a,the exposed ends of insert 360 are bent backward in grooves 28a anddeformed to the shape 37a, best shown in FIGS. 7 and 8, therebyfrictionally impeding separation of the two members as in the precedingmodification. Rearward movement of blade 11a is limited by the length ofgrooves 51, which are of reduced depth at their proximal ends. When itis desired to replace the blade, it may be driven off of the holder in away similar to that explained with reference to FIGS. 1-4.

Turning now to the modification shown in FIGS. 9-12 inclusive, it willbe seen that the blade 11b and holder 12b are generally similar to thepreceding modification. Corresponding elements have been designated withthe same reference numeral followed by the suflix b.

The cross-sectional shape of the opening 41!) in the proximal end ofblade 11b is dovetail-shaped in that there is a substantially horizontaltop surface 461) and downwardly converging side surfaces 42b.

The forward portion 13b of holder 12b has its upper portioncomplementary to the dovetail opening 41b in the blade Thus there is aflat top surface 53b and downwardly converging sidewalls 55 providing aweb 5222 through which extends hole 27b. The depth of opening 41!) issuch that the forward end 56 abuts and is limited in forward movement bythe front wall 57 of said opening 41b. It will be understood, however,that other means may be employed to limit movement of blade 11b relative to holder 12b.

The modification of FIGS. 13-16 is quite similar to that of FIGS. 912except for the shape of opening 41c and the corresponding complementaryshape of web 520. Corresponding elements have been designated with thesame reference numeral followed by the sufiix c. In this form of theinvention the shape of the complementary portions is a flattened ortruncated oval. Thus the top wall 46c is fiat and horizontal and thesidewalls 420 are oval, or inwardly curved rather than flat and straightas in the preceding modification. The lower end 500 of end 130 issubstantially rectangular, although other shapes are also useful.Further, the web 520 has a top surface 530 and convex oval side walls55c. The function of the resilient insert 360 is the same as in thepreceding modification.

In FIGS. 5 to 16 inclusive, various cross-sectional shapes of the holderweb and opening are illustrated. It will be understood that othershapes, such as round, full or partial oval or rectangular may be used.Further, in FIGS. 1-4 a shape complementary to the shape of FIGS. 58 isused. It will be understood that shapes complementary to that in theother modifications illustrated as previously mentioned also may besubstituted.

The modification of FIGS. 17-23 are similar to the precedingmodifications. The blade 71 is a harrow blade or a blade performing asimilar function. Thus the blade 71 may be a plow or scarifier blade ora cable plow used in forming a furrow for installation of electricalcable. A vertical shank 72 of extended length is conventionally used tosupport blade 71, being fastened as by means of U-bolt 73 to astructural member 74 of the machine. Blade 71 is preferably formed withtips 76 at either end so that the blade may be reversed when one end isdull or broken. The lower end 77 of shank 72 is curved forwardly andblade 71 is curved to fit the curvature of the shank. Conventionallysuch blade 71 is bolted by means of a bolt (not shown) to the lower endof shank 72 to permit removal for replacement or inversion. The use ofsuch a bolt is undesirable in that it weakens the blade, the fasteningmeans may become disengaged or other difficulties occur. The use of thebolt is eliminated in accordance with the present invention.

Fitting 81 is welded as by welds 80 or otherwise secured to the back ofblade 71. Fitting 81 is disposed longitudinally of the blade and ispreferably of considerably lesser length than the blade. Incross-section extension 81 is T-shaped having a leg 82 of restrictedwidth which is connected at its proximal end to blade 71 as by weldingor integrally formed. Laterally extending arms 83 extend normal to leg82. One or more holes 84 are formed transversely through leg or web 82,preferably there being one hole 84 adjacent each end of leg 82.Intermediate holes 84, or in any event communicating with each hole 84,is a groove 86 formed in the side wall 87 of leg 82. The cross-sectionalshape of groove 86 as compared to hole 84 is in the same relationship asin the preceding modifications. In this form of the invention aresilient insert 88 of a shape such as to fit within one of holes 84 andof a length considerably greater than the width of leg 82 is used, thematerial of construction being the same as in the precedingmodifications.

To receive fitting 81, the top surface of portion 77 is formed with aslot 91 having side walls 92 parallel to walls 87 and spaced apart adistance slightly greater than walls 87. Below side walls 92 are lateralextensions 93 which are dimensioned to receive arms 83.

In use, the particular point 76 which is to be the working point isplaced downwardly and a resilient insert 88 inserted in the particularhole 84 remote from the point 76 in use. The ends of insert 88 projectout beyond holes 84. The blade 71 is then assembled on shank 72, thefitting 81 being received in opening 91. As the blade is pushed backwardthe resilient insert 88 is compressed into grooves 86 and deformed inportions 94 as in the preceding modification. Removal of blade 71 isaccomplished by hammering down on the point 76 not in use untilfrictional resistance is overcome.

Although a curved blade 71 is illustrated in the accompanying drawings,it will be understood that a flat blade may be used in cable plows andother installations. Plural inserts 88 may be used where required byreason of severe operating conditions.

FIGS. 19A and 20A show a modification of the structure of FIGS. 17-21,wherein holes 84 and grooves 86 in fitting 81 are eliminated. A pair ofholes 96 is formed in the thickened portions 97 above arms 83a, saidholes 96 being located near the distal end 77a of the shank. Grooves 98are formed in portions 97 facing side walls 87a. The dimensionalrelationship between grooves 97 and holes 96 is as previously defined. Aresilient insert 88a: is placed in one or both holes 96 prior to fitting81a being inserted in slot 91a. The function of insert 88a is the sameas in the preceding modifications and removal of the blade is similarlyaccomplished. Since many of the elements are very similar to those ofFIGS. 17-21, the same reference numerals followed by sufiix a are used.

Although the foregoing invention has been described in some detail, byway of illustration and example for purposes of understanding, it isunderstood that certain changes and modifications may be practicedwithin the spirit of the invention and scope of the appended claims.

What is claimed is:

1. In earth digging equipment, a blade holder member, a blade member anda resilient retainer for said members, a first of said members formedwith a recess having at least one first wall, a second of said membersformed with an extension complementary to said recess and having atleast one second wall facing and in close proximity to said first wall,said extension sliding longitudinally into said recess, at least onesaid wall formed with a longitudinaly extending groove and a transversehole, said retainer fitting in said hole and being compressed into saidgroove to frictionally restrain longitudinal relative movement of saidmembers, said recess and said extension being T-shaped in cross-sectionhaving a leg and transverse feet and one said wall extending along saidleg, said hole normal to said leg, said extension being completelyenclosed within said recess, the walls of said recess surrounding saidleg and said feet, said groove having a cross-sectional areasubstantially less than the initial uncompressed cross-sectional area ofsaid retainer, said groove being substantially wider in a directiontransverse to the direction of insertion of said blade member in saidblade holder member than the depth of said groove, whereby thecompressed shape of said retainer provides an extend surface offrictional contact between said members.

2. The combination of claim 1 in which said blade member is formed withsaid extension, said hole transverse through said leg.

3. The combination of claim 1 in which said blade member is formed withsaid extension, said hole formed in said blade holder member transverseto said leg.

4. The combination of claim 1 in which said blade member is formed withsaid recess and said blade holder member is formed with said extensionand said extension formed with a bottom portion below said leg engagingthe underside of said blade member, said hole transversely through saidleg and said groove in a side of said leg.

5. In earth digging equipment, a blade holder member, a blade member anda resilient retainer for said members, said blade member formed with adove-tailed recess having at least one first wall, a second of saidmembers formed with a dovetailed extension complementary to said recessand having converging side walls, at least one side wall facing and inclose proximity to said first wall, said extension slidinglongitudinally into said recess, at least one said side wall formed witha longitudinally extending groove, a transverse hole between said sidewalls, said retainer fitting in said hole and being compressed into saidgroove to frictionally restrain longitudinal relative movement of saidmembers, said groove having a cross-sectional area substantially lessthan the initial uncompressed crosssectional area of said retainer, saidgroove being substantially wider in a direction transverse to thedirection of insertion of said blade member in said blade holder memberthan the depth of said groove, whereby the compressed shape of saidretainer provides an extended surface of frictional contact between saidmembers.

6. In earth digging equipment, a blade holder member, a blade member anda resilient retainer for said members, said blade member formed with arecess of truncated oval cross-section having at least one first wall,said blade holder member formed with an extension of oval crosssectioncomplementary to said recess having inwardly curved side walls andhaving at least one said side wall facing and in close proximity to saidfirst wall, said extension sliding longitudinally into said recess, atleast one said side wall formed with a longitudinally extending grooveand a transverse hole between said side walls, said retainer fitting insaid hole and being compressed into said groove to frictionally restrainlongitudinal relative movement of said members, said groove having across-sectional area substantially less than the initial uncompressedcross sectional area of said retainer, said groove being substantiallywider in a direction transverse to the direction of insertion of saidblade member in said blade holder member than the depth of said groove,whereby the compressed shape of said retainer provides an extendedsurface of frictional contact between said members.

7. In earth digging equipment, a blade holder member, a blade member anda resilient retainer for said members, said blade member formed with arecess, said recess of non-circular shape having a pair of first walls,said blade holder member formed with an extension of non-circular shapecomplementary to said recess and having a pair of second walls facingand each in close proximity to a first wall, said extension slidinglongitudinally into said recess, at least one said second wall formedwith a longitudinally extending groove and a transverse hole betweensaid second walls, said retainer fitting in said hole and beingcompressed into said groove to frictionally restrain longitudinalrelative movement of said members, said groove having a cross-sectionalarea substantially less than the initial uncompressed cross-sectionalarea of said retainer, said groove being substantially wider in adirection transverse to the direction of insertion of said blade memberin said blade holder member than the depth of said groove, whereby thecompressed shape of said retainer provides an extended surface offrictional contact between said members.

8. The combination of claim 1 which further comprises an extended toothsecured to said blade member, said tooth extending longitudinally, saidextension being on said blade member and of substantially lesser lengththan said tooth.

The combination of claim 8 in which said blade is reversible end to endand said extension is reversibly insertable in said recess.

10. The combination of claim 9 in which one said hole is formed adjacenteach end of said extension, said groove on said extension.

11. The combination of claim 9 in which said extension has one holeformed in said leg adjacent either end of said extension, said grooveformed 011 the side of said leg.

12. The combination of claim 9 in which said hole is formed in saidblade holder perpendicular to and intersecting said leg, said groove insaid blade holder extending longitudinally opposite said leg.

References Cited UNITED STATES PATENTS 775,770 11/1904 Herrod 172751 X2,222,071 11/ 1940 Gustafson 37142 X 2,968,880 1/1961 Petersen 37-1423,057,091 10/1962 Petersen 37-142 ABRAHAM G. STONE, Primary Examiner.

A. E. KOPECKI, Assistant Examiner.

1. IN EARTH DIGGING EQUIPMENT, A BLADE HOLDER MEMBER, A BLADE MEMBER ANDA RESILIENT RETAINER FOR SAID MEMBERS, A FIRST OF SAID MEMBERS FORMEDWITH A RECESS HAVING AT LEAST ONE FIRST WALL, A SECOND OF SAID MEMBERSFORMED WITH AN EXTENSION COMPLEMENTARY TO SAID RECESS AND HAVING ATLEAST ONE SECOND WALL FACING AND IN CLOSE PROXIMITY TO SAID FIRST WALL,SAID EXTENSION SLIDING LONGITUDINALLY INTO SAID RECESS, AT LEAST ONESAID WALL FORMED WITH A LONGITUDINALLY EXTENDING GROOVE AND A TRANSVERSEHOLE, SAID RETAINER FITTING IN SAID HOLE AND BEING COMPRESSED INTO SAIDGROOVE TO FRICTIONALLY RESTRAIN LONGITUDINAL RELATIVE MOVEMENT OF SAIDMEMBERS, SAID RECESS AND SAID EXTENSION BEING T-SHAPED IN CROSS-SECTIONHAVING A LEG AND TRANSVERSE FEET AND ONE SAID WALL EXTENDING ALONG SAIDLEG, SAID HOLE NORMAL TO SAID LEG, SAID EXTENSION BEING COMPLETELYENCLOSED WITHIN SAID RECESS, THE WALLS OF SAID RECESS SURROUNDING SAIDLEG AND SAID FEET, SAID GROOVE HAVING A CROSS-SECTIONAL AREASUBSTANTIALLY LESS THAN THE INITIAL UNCOMPRESSED CROSS-SECTIONAL AREA OFSAID RETAINER, SAID